In a wireless communication system, inter-symbol interference (ISI) between received signals is usually caused by a multi-path fading effect in a radio channel. To remove the ISI, a receiver is provided with an equalizer that needs information of channel impulse response (CIR) to operate, and therefore estimation of the CIR plays a critical part in a mobile radio system. In an Orthogonal Frequency-Division Multiplexing (OFDM) communication system, data symbols may be analyzed according to a predetermined pilot symbol known by a transmitter and a receiver in the estimation of CIR. The pilot symbol is carried by a pilot sub-carrier, and a carrier index of the pilot sub-carrier is compliant to a pilot pattern of a digital signal system specification. For example, in the European Digital Video Broadcasting—Second Generation Terrestrial (DVB-T2) specification, pilot patterns are divided into eight pattern types of PP1, PP2 . . . and PP8 according to different Fast Fourier Transform (FFT) sizes and different guard intervals. Sub-carrier indexes of a same pilot pattern may be different according to different carrier modes. For example, carrier modes of the DVB-T2 specification include a normal carrier mode and an extended carrier mode; the extended carrier mode that applies more frequency-domain sub-carriers than the normal carrier mode is capable of transmitting more data. Therefore, how to accurately detect a pilot pattern and a carrier mode in channel estimation stands as an important subject.
In addition, in a communication system, a mixer up-converts a signal at a transmitting end to a radio frequency (RF) signal that is then transmitted, and the RF signal received at a receiving end via an antenna is down-converted to a baseband signal to be processed. Due to frequency discrepancy between oscillators at the transmitting end and the receiving end, the frequency-reduced signal received at the receiving end has a carrier frequency offset that undesirably affects the accuracy in processing the baseband signal. The carrier frequency offset is a result of an integer carrier frequency offset (ICFO) plus a fractional carrier frequency offset. The ICFO signifies that a frequency offset at the receiving end is an integer multiple of a carrier spacing, and the fractional carrier frequency offset signifies that the frequency offset at the receiving end is a fraction of the carrier spacing. Therefore, an apparatus for detecting a carrier frequency offset is needed to calibrate the frequency-reduced signal of the mixer at the receiving end to an accurate baseband frequency.
In view of the foregoing issues, a digital video signal parameter detecting apparatus capable of simultaneously detecting an ICFO, a pilot pattern and a carrier mode of a received signal at a receiving end is in need to achieve an object of calibrating a frequency at the receiving end and parameters needed for detecting a channel estimation module, as well as reducing chip cost and a signal processing time.